How to Make It
In a large saucepan of boiling salted water, cook the beans, stirring a few times, until just tender, about 5 minutes. Drain and refresh under cold water. Pat dry thoroughly with paper towels.
In a large bowl, whisk the lime juice with the olive oil, lime zest, and salt. Add the beans and toss. Add the red onion and toss again. Serve at once.